## Summary
Under Vite's experimental `bundledDev` mode, the `hotUpdate` hook in
`@tailwindcss/vite` gets called without a `server`. Vite only passes `{
type, file, modules }` here, but the hook loops over
`Object.values(server.environments)`, so editing any file (JS, CSS, or
HTML) throws `TypeError: Cannot read properties of undefined (reading
'environments')` and the dev server build fails.
The fix returns early when `server` is missing. Those environment loops
only look at environments other than the current one, and the
server-level `hot`/`ws` reload channels don't exist in this mode, so
bailing out leaves the classic (non-`bundledDev`) dev path untouched.
Fixes#20378
## Test plan
- Added a unit test that calls `hotUpdate` without a `server` and checks
it doesn't throw. It fails on the current code and passes with the
guard.
- Reproduced with a Vite 8 project using `experimental.bundledDev:
true`: before the change, editing any JS/CSS/HTML file crashed the dev
server; after it, edits work.
- `pnpm run test` and the `@tailwindcss/vite` integration suite both
pass.
[ci-all]
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Co-authored-by: Robin Malfait <malfait.robin@gmail.com>
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